truck will start then stall

put my truck in a ditch on its driver side water 6-10 inches in the cab...new lock key cylinder was installed(broke key in old when climbing out). truck will now start then stall right after.

latest update we plugged in a tech II gm reader (my dad and i) when we go into the body control module(bcm) 3 codes came up one being the theft thing.I dont know how to get around it..If anyone knows lemme know lol thanks

You probably allready fixed this, but you need to perform a security re-learn procedure... put the key in the ignition and turn to on (but not start). Leave it for 10 minutes (security light should go solid I think). Turn off for 10 seconds. Repeat this procedure twice more (for a total of 30 minutes) and then after that start the vehicle. That re-learns the new key/cylinder and you should be good to go.